There are many types of automatic and semi-automatic rifles currently in use, which may be used by both military personnel as well as civilians. For modern military uses, the generally smaller size and lighter weight of carbine rifles offers an advantage due to the rifle being easier to handle and also more maneuverable in close quarters battle, such as in urban settings. For instance, M4 carbine rifles are commonly used by the United States Armed Forces as a replacement for the M16 assault rifle as a standard issue primary infantry weapon to combat units due to its shorter barrel, which makes the rifle easier to handle for infantrymen. However, a standard M4 is about 33 inches in length with the stock extended and has an empty weight of about 6.5 pounds. Thus, in order to make the rifle lighter and more maneuverable, it would be advantageous to further reduce the length and weight of the rifle. However, simply shortening the barrel length of current M4 models would decrease muzzle velocity and generally reduce ballistic performance, particularly at longer ranges.
A limiting factor in reducing the size of a rifle such as an M4 is a minimum required barrel length as well as the types of firearm cartridges used by such rifles. Firearm cartridges have seen little improvement since the creation of the centerfire round. Today projectiles are seated in a cartridge casing so that the majority of the projectile is outside the open end of the casing. The common perception is that the increased pressure of firearm cartridges having deeply seated projectiles is undesirable. As a result, the length of many rifle rounds is too long for a rifle design where a magazine may be inserted through the handle. This results in an increased length of the rifle since the stock must be longer to compensate for the handle being placed closer to the rear end of the receiver. Because increased rifle length is undesirable in close quarters combat, often times the barrel length is reduced so that the firearm is more suitable for close quarters combat.
Accordingly, a need exists in the art for an improved firearm cartridge and a rifle designed to fire the cartridge so that the length of a rifle may be reduced without decreasing the length of the barrel.